One of my favorite blogs, scientificblogging, recently posted an article about a sleep disorder with arresting implications -- it's called sexsomnia, a form of non-Rapid Eye Movement (NREM) parasomnia that causes people to engage in sexual acts while they are asleep, more often than not with no memory of the event, similar to sleepwalking. Both men and women may be afflicted. The condition has been linked to incidents of rape, unintended sex with strangers, and physical injury to oneself. Aggravating factors include alcohol and sleep deprivation.
Sexsomnia, or sleep sex, has only become a recognized diagnosis within the past 15 years. Since the person with the disorder rarely remembers an episode, it is usually noted first by his/her partner. Feelings of shame or embarrassment prevent many from reporting such incidents, since most aren't aware that theirs is not a unique occurance. Diagnosis cam be confirmed using polysomnography during a night spent in a sleep lab. Sadly, most cases only come to light only after criminal charges have been filed. Nevertheless, the majority of events occur in the home and involve no crime.
Please check out the article link for a more thorough description.